In the related art, an air-conditioning apparatus exists which transports a cooling energy or a heating energy to an air conditioning target area such as an indoor area by circulating refrigerant between outdoor unit as heat source unit disposed in an outdoor area and indoor unit disposed in an indoor area, thereby executing a cooling operation or a heating operation. For example, for structural use in buildings or the like, there is a building multi-air conditioner in which one or plural outdoor unit and plural indoor unit are connected to each other via pipes to circulate the refrigerant (for example, see Patent Literature 1). As the refrigerant used in the air-conditioning apparatus, for example, an HFC-based refrigerant is widely used. Furthermore, in recent years, a natural refrigerant such as carbon dioxide (CO2) has also been used.
Furthermore, an air-conditioning apparatus of another configuration represented by a chiller system also exists. In the air-conditioning apparatus, the cooling energy or the heating energy is created in the heat source unit disposed in an outdoor area, the heating energy or the cooling energy is transmitted to water, anti-freezing fluid or the like by a heat exchanger disposed in the outdoor unit and is transported to a fan coil unit, a panel heater or the like which is the indoor unit disposed in the air conditioning target area, thereby executing the cooling operation or the heating operation (for example, see Patent Literature 2). In addition, there is also an air-conditioning apparatus in which four water pipes are connected to heat source unit called a waste heat recovery type chiller to supply the cooling energy and the heating energy.